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Before the age of space exploration, astronomers assumed that the Moon's core was smaller than the Earth’s, in both relative and absolute terms – the radius of the Earth's core is 55 percent of the overall radius of the Earth and the core's mass is 32 percent of the Earth's overall mass – but they had no way to verify this. Two sets of data gathered by Lunar Prospector have now given astronomers the ability to determine that the Moon's core accounts for 20 percent of the Moon's radius and for a mere 2 percent of its overall mass. First, scientists measured minute, relatively rapid variations in the wavelength of radio signals from Lunar Prospector as the craft moved towards or away from the Earth. Using these variations, scientists accurately determined even slight changes in the craft's velocity while the craft orbited the Moon, changes resulting from inconsistency in the gravitational pull of the Moon on the craft. The data were used to create a "gravity map" of both near and far sides of the Moon, highlighting new details of the distribution of the Moon's internal mass. Scientists thus determined that the Moon has a small, metallic core, which, if composed mostly of iron, has a radius of approximately 350 kilometers. The second method involved examining the faint magnetic field generated within the Moon itself by the Moon's monthly passage through the tail of the Earth's magnetosphere. This approach confirmed the results obtained through examination of the gravity map. The size and composition of the Moon's core have serious implications for our understanding of the Moon's origins. If the Moon and Earth developed as distinct entities, the sizes of their cores should be more comparable. In actuality, it seems that the Moon was once part of the Earth and broke away at an early stage in the Earth's evolution, perhaps due to a major asteroid impact that could have loosened a chunk of iron, allowing it to form the core around which the Moon eventually coalesced. Alternatively, according to fission theory, the early Earth may have spun so rapidly that it ejected a quantity of material by so-called centrifugal force, material that later coalesced by mutual gravitational attraction into the Moon.

Questions -->1. It can be inferred from the passage that the impact theory and the fission theory of the Moon’s origin are similar in that they botha. explain the congruence in the size and mass of the Earth’s and the Moon’s coresb. assert that the Moon did not predate the Earthc. imply the development of the Earth and Moon as distinct entitiesd. propose that iron ejected from the Earth coalesced the rest of the Moon through magnetic attractione. account for the inconsistency in the gravitational pull of the Moon

2. The primary purpose of the passage is best expressed in which of the following ways?a) The author presents the data set that proved that the Moon was once part of the Earth.b) The author discusses the data sets that changed scientists' opinions about the relative sizes of the Earth's and the Moon's cores.c) The passage analyzes the assumptions about radii and core mass that led to important implications about the origin of the planets.d) The passage examines the use of scientific methods to analyze data and confirm a hypothesis, while referencing possible deductions.e) The passage elucidates the implications following from the size of the Earth's core.

3. If the wavelength of radio signals emitted by the Lunar Prospector were constant, then which of the following could be most properly inferred?a) The velocity of the spacecraft depends on whether it is on the near or far side of the Moon.b) The size and mass of the Moon’s core may be more comparable to the size and mass of the Earth’s core than is currently believed.c) As the craft orbits the moon, the Moon exerts a constant gravitational pull on the craft.d) The Earth and the Moon seem to have originated independently.e) It would be impossible to create a gravity map of the Moon.

Before the age of space exploration, astronomers assumed that the Moon's core was smaller than the Earth’s, in both relative and absolute terms – the radius of the Earth's core is 55 percent of the overall radius of the Earth and the core's mass is 32 percent of the Earth's overall mass – but they had no way to verify this. Two sets of data gathered by Lunar Prospector have now given astronomers the ability to determine that the Moon's core accounts for 20 percent of the Moon's radius and for a mere 2 percent of its overall mass. First, scientists measured minute, relatively rapid variations in the wavelength of radio signals from Lunar Prospector as the craft moved towards or away from the Earth. Using these variations, scientists accurately determined even slight changes in the craft's velocity while the craft orbited the Moon, changes resulting from inconsistency in the gravitational pull of the Moon on the craft. The data were used to create a "gravity map" of both near and far sides of the Moon, highlighting new details of the distribution of the Moon's internal mass. Scientists thus determined that the Moon has a small, metallic core, which, if composed mostly of iron, has a radius of approximately 350 kilometers. The second method involved examining the faint magnetic field generated within the Moon itself by the Moon's monthly passage through the tail of the Earth's magnetosphere. This approach confirmed the results obtained through examination of the gravity map. The size and composition of the Moon's core have serious implications for our understanding of the Moon's origins. If the Moon and Earth developed as distinct entities, the sizes of their cores should be more comparable. In actuality, it seems that the Moon was once part of the Earth and broke away at an early stage in the Earth's evolution, perhaps due to a major asteroid impact that could have loosened a chunk of iron, allowing it to form the core around which the Moon eventually coalesced. Alternatively, according to fission theory, the early Earth may have spun so rapidly that it ejected a quantity of material by so-called centrifugal force, material that later coalesced by mutual gravitational attraction into the Moon.

1. It can be inferred from the passage that the impact theory and the fission theory of the Moon’s origin are similar in that they both

a. explain the congruence in the size and mass of the Earth’s and the Moon’s coresb. assert that the Moon did not predate the Earthc. imply the development of the Earth and Moon as distinct entitiesd. propose that iron ejected from the Earth coalesced the rest of the Moon through magnetic attractione. account for the inconsistency in the gravitational pull of the Moon

2. The primary purpose of the passage is best expressed in which of the following ways? a) The author presents the data set that proved that the Moon was once part of the Earth.b) The author discusses the data sets that changed scientists' opinions about the relative sizes of the Earth's and the Moon's cores.c) The passage analyzes the assumptions about radii and core mass that led to important implications about the origin of the planets.d) The passage examines the use of scientific methods to analyze data and confirm a hypothesis, while referencing possible deductions.e) The passage elucidates the implications following from the size of the Earth's core.

3. If the wavelength of radio signals emitted by the Lunar Prospector were constant, then which of the following could be most properly inferred?

a) The velocity of the spacecraft depends on whether it is on the near or far side of the Moon.b) The size and mass of the Moon’s core may be more comparable to the size and mass of the Earth’s core than is currently believed.c) As the craft orbits the moon, the Moon exerts a constant gravitational pull on the craft.d) The Earth and the Moon seem to have originated independently.e) It would be impossible to create a gravity map of the Moon.

Wavelength of radio signals was used to find velocity variations. These velocity changes were then used to deduce information about gravitational pull. If the wavelength would have been constant, then the scientists would have inferred that Lunar Prospector is moving with uniform velocity. Thus, they would have concluded that the moon exerts uniform gravity on the craft.

This answer is incorrect because it disregards the earth's gravitational affect on the speed of the craft. The craft would actually "slingshot" as it passed the far side of the moon where the earth's gravity and the moons gravity work in uniform to cause an elliptical orbit. Any physics majors want to weigh in here?